Method for on-line monitoring and control of the performance of an electric arc furnace

• US 5,099,438 A
• Filed: 08/28/1989
• Issued: 03/24/1992
• Est. Priority Date: 08/28/1989
• Status: Expired due to Term

• Current Assignee: Ucar Carbon Technology Corporation
• Original Assignee: Ucar Carbon Technology Corporation
• Inventors: Penkal, Kenneth W., Gulden, George Jr.
• Primary Examiner(s): Dixon, Joseph L.
• Application Number:
  US07/398,968
• Time in Patent Office: 939 Days
• Field of Search: 364/550, 364/551.01, 364/505, 364/506, 364/514, 373/1, 373/2, 373/102, 373/104, 373/105, 373/106, 370/99, 340/870.01, 340/870.17, 340/521, 340/534, 340/825.29, 340/825.50, 340/825.53, 340/825.08
• US Class Current: 700/274
• CPC Class Codes: G05B 19/058 Safety, monitoring
• CPC Class Codes: H05B 7/148 Automatic control of power electrode feeding arrangements H05B7/109; automatic feeding of electrodes for spot or seam welding or cutting B23K9/12; disposition of electrodes in or on furnaces F27D11/10; control of position in general G05D3/00; regulating electric characteristics of arcs in general G05F1/02; regulating electric power in general G05F1/66
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A method for on-line monitoring and/or control of an electric arc furnace utilizing a method of data transfer between a programmable logic controller and a microprocessor comprising monitoring data from the furnace over a fixed time cycle, assigning data values to the monitored data during such time cycle, dividing the fixed time cycle into a multiple of N time subintervals, dividing the data values into data subsets, assigning designated time subintervals to each of the data subsets, transmitting data to the microprocessor in each time subinterval to execute program code corresponding to the data subset in such time subinterval and calculating control factors from the transmitted data for providing control information.

Claims

1. A method for on-line monitoring and control of an electric arc furnace in the manufacture of steel using a data processing system for providing control information to control the electric arc furnace comprising the steps of:

(a) monitoring electrical data from the arc furnace representative of the electrical conditions and electrical power delivered to the furnace;

(b) calculating a Stability Factor (SF) from said electrical data in accordance with the following algorithm;

##EQU8## Short Circuit Reactance=Constant which is derived by submerging the electrodes into the liquid steel bath and performing the following calculation;

##EQU9## Where;

Megvars=measured primary reactive power;

Current=measured average primary current

N=transformer voltage ratio

(c) comparing said calculated

Stability Factor with a pre-established Stability Factor for said arc furnace corresponding to a given period of furnace operation; and

(d) introducing raw material into the furnace when the calculated Stability Factor is below the pre-established level for said period of furnace operation to raise the Stability Factor to said pre-established level.

2. A method for on-line monitoring and control of the performance of an electric arc furnace in which an electric arc is established between a plurality of graphite electrodes and a charge of metal in the manufacture of steel, with power to the furnace supplied from a power supply having a three phase transformer for melting and refining said charge under conditions in which a foamy slag is formed above the liquified metal during the period of metal refining, comprising the steps of:

(a) monitoring electrical data from the arc furnace representative of the electrical conditions and electrical power delivered to the furnace;

(b) measuring the primary reactive power on the primary side of said three phase transformer;

(c) calculating a Stability Factor (SF) from said electrical data in accordance with the following algorithm;

##EQU10## Where;

##EQU11## Short Circuit Reactance=Constant which is derived by submerging the electrodes into the liquid steel bath and performing the following calculation;

##EQU12## Where;

Megavars=measured primary reactive power;

Current=measured average primary current

N=transformer voltage ratio

(d) periodically compiling a report of furnace conditions wherein one entry in said report is said Stability Factor;

(e) monitoring said Stability Factor; and

(f) varying said foamy slag in said furnace in response to the monitored level of said Stability Factor.

3. A method as defined in claim 2 wherein said foamy slag is varied by the addition of oxygen and/or coke.